1. Field of the Invention
The present invention relates generally to wall and/or panel systems and, more particularly, is concerned with a new and improved insulated panel system for storage tanks.
2. Description of the Prior Art
In the petroleum and chemical industries it is customary to store liquids and the like within large tank structures which are usually installed out in the open where they are exposed to the elements, both heat and/or cold. These storage facilities usually comprise circular steel or other metallic tank structures which by reason of being installed out in the open, must be provided with a suitable insulating material so that the products in storage within the storage tanks may be kept at the desired temperatures. In storage tank insulation systems, it has thus been customary to apply some type of an insulating material exteriorly of the metallic tank structure and to securely bind the same thereto by the use of an adhesive or by circumferential bands extending completely around the outside diameter of the tank and secured in a fixed position. Various arrangements or systems have been provided in the past for securing insulated panels to storage tanks. Representative patents in the general area of securing insulated panels to storage tanks are U.S. Pat. Nos. 2,323,297 (heat insulating construction); 2,501,951 (construction of tanks, silos, and like vessels); 3,456,835 (thermally insulated tank structure); 4,004,394 (method for insulation of curved surfaces); 4,044,517 (insulated tank jacketing system); 4,338,756 (panel and insulation system); 4,347,949 (insulated tank).
The manner of securing insulating panels to the exterior of a metallic storage tank has inherent problems for the reason that the tank structure is often times exposed to varying temperature gradients with the result that the metallic shell is caused to expand and contract due to such temperature variations. If an insulating material has been applied to the exterior surface of such a tank as by adhesively securing the same thereto, the adhesive bond between the metallic shell and insulating material is caused to be broken due to such expansion and contraction with the result that the insulating material is separated from the metallic shell with resultant loss of insulation for the tank at such spots and areas. In instances where the insulating material is secured to the tank structure as by means of exteriorly extending circumferential bands, the bands are usually set to a pre-tensioned force at the time of installation of the insulating material and when, by reason of differing temperature gradients, the tank walls are caused to expand and/or contract, the bands, which are usually formed of metal are incapable of further stretching to accommodate the expansion of the tank and insulating material thereof and will break or snap off thus necessitating the repair or replacement of such bands. On the other hand, where the tank structure is caused to contract, the metallic bands lose their efficiency as holding means for the insulating material since the bands are not exposed to the temperatures within the tank which causes such contraction of the metallic tank. Other arrangements have including welding anchoring studs to the outside wall of the tank structure and then fastening the insulated panels to these anchoring studs by means of metal screws or metal fasteners. The difficulty with such an arrangement is that at times the stud welding operation can expose explosion hazards, or the condition of a given tank wall is such that it would not readily accept a stud weld. Another draw back is that due to the expansion and contraction of the metal panels, the metal fasteners are worked out of the anchoring studs and thus the panels become loose.
One system concerned with the application of insulated panels to storage tank structures is described and illustrated in U.S. Pat. No. 4,122,640 to Commins, et al. The Commins, et al patent discloses an insulated tank jacketing system comprising panels having opposed side flanges, one of which includes a terminal bead and the other which includes a deformable sleeve that can be folded tightly about the bead of a similarly configured and adjacent channel section with an articulated fastener securing a pair of panel sections to a stranded wire cable, said fastener comprising a link element interposed between the side flanges of the adjacent panel sections and provided at one extremity with a bulbous rivetlike element insertable within and engageable with the interior wall of the bead of one panel section about which the sleeve of the adjacent panel section is folded.
While this system, or variations of it, can be used for an insulated tank jacketing system, it does have serious draw backs. First, the panel system described in Commins, et al involves greater costs in materials, labor and installation and greater inflexibility in panel design. The panels comprise upstanding and opposing side flanges each having a unique shape one of which includes a terminal bead and the other which includes a deformable sleeve that can be folded tightly about the terminal bead on a similarly configured and adjacent side panel. The unique features of the side flanges require greater costs in production. Since they are of a fixed shape, they cannot vary in width and cannot be shaped or formed at the job site. It would thus be advantageous for a panel system to employ simple panels that can very in length and width with straight opposed side flanges that could be formed at the job site for any length and width desired. This would result in a reduction of production costs of the panels and greater flexibility in on site designing and installation of the system. Second, the fasteners of the Commins, et al patent are more expensive to manufacturer and produce due to the unique shape of the articulated fastener and the various parts involved. The fastener has inherent features which could fail. Due to the constant expansion and contraction of all the components parts of the system, the rivet pin and/or the aluminum bulbous elliposoidal element plug could work or fall out causing the panels to become loose. Further, it takes time to install these fastening elements and special pneumatic or manual crimping tools are required to install these fastening elements both on the cable and within the terminal bead. It would thus be advantageous to employ an inexpensive continuous fastener which could be installed quickly without the necessity of special tools thus reducing labor costs. Third, the installation of the insulated tank jacketing system described in Commins, et al is labor intensive. The aluminum bulbous elliposoidal element plug of the fastening element must first be inserted into the mouth of the elongated bead section of one flange section, next the clamp portion of the fastening element must be crimped around the cable by use of a special pneumatic or hand crimping tool, next the elongated beaded section of the flange needs to be slightly crimped or collapsed on the opposite sides of the aluminum bulbous elliposoidal element plug by use of a crimping tool to prevent slippage, next the elongated sleeve of the adjacent panel flange must be folded about the elongated bead section of the previous panel by means of an electric power tool or the like provided with crimping rollers that engage the sleeve of the second panel and progressively crimp it about the elongated bead section of the flange. Obviously, this is very time consuming. It would be advantageous to again have an inexpensive continuous fastener which could be installed easily around the cable and attached to the side flanges without the use of any special pneumatic or manual crimping tools. Fourth, the method of attachment of the fastening elements could prevent cable movement and cause harmful stresses to build up within the cable. By utilizing stranded wire cables, the tank and wire cables will expand substantially uniformily relative to each other. The cable must be allowed to expand, roll or uncoil in the expansion process so that no undue stresses or movements will be imposed on the jacketing system and the components thereof. The fastening element in Commins, et al contemplates tightly crimping the base of the fastening element about the stranded cable. By doing so, this will prevent the cable from rolling or moving under expansion and could possibly cause deformation of the panels if the rivet pin in the fastening element stuck or failed for any reason. The Commins, et al patent further teaches that the base of the fastening element could be provided with a pair of anti-rotation wing-like tabs or prongs that could be adapted to rest against the wall of the tank so as to prevent any severe rotation of the clamp and fastening element. These anti-rotational wing-like tabs would also prevent any desired and required rotational movement or expansion of the cable relative to the tank which would prevent any undue stresses from building up in the cable. It would thus be advantageous for a fastening element to be employed in such a manner that would not restrict the expansion and contraction or rotational movement of the cable in any way but also firmly attach the panel section to the cable. Fifth, the method of joining adjacent flanges of panels sections together could possibly cause seam leakage and panel separation. The method taught in Commins, et al contemplates that the beaded section of the first flange is slightly crimped or collapsed on opposite sides of the aluminum bulbous elliposoidal element plug. This crimping leaves open air spaces in the form of two indentations on the surface of the beaded flange section. Thereafter, the elongated sleeve of the flange on the adjacent panel is folded about the elongated bead and over the indentations produced therein by means of an electric power tool which folds the elongated sleeve flange section over the elongated bead flange section. Thus, the intersurface of the elongated sleeve flange section is not flush against the outersurface of the elongated bead flange section. The indentations between the surfaces create open air spaces which could collect moisture and lead to rust, corrosion and overall weakening of the panel system. The constant expansion and contraction of the panels due to changes in temperature and hydrostatic pressures resulting from filling and emptying the tanks with liquids, etc., could cause the folded over sections of the flanges to open up over these indentations which could lead to loosing of the panels, leakage between the panels and possible corrosion of the tank wall. It would thus be advantageous to provide a continuous tight seal between the flanges on adjacent panel sections with no internal open air spaces between them.
Consequently, a need exists for improvements in insulated tank jacketing systems over the Commins et al patent which would solve the problems heretofore mentioned above by providing a totally closed sealed insulation jacketing system having no restriction of movement on any component part thereof and which would: result in greater reduction of material, labor and installation costs; provide for greater flexibility in on-site panel design and installation at reduced costs; allow for adequate expansion and contraction and movement of all parts of the jacketing system without build up of undue stresses; and produce a tighter seal between the adjacent panel flanges with no internal open air spaces.